The present invention relates to a high-pressure fuel accumulator for a common-rail fuel injection system of an internal combustion engine, having a tubular main body to which is welded at least one bushing for connecting a high-pressure line.
A high-pressure fuel accumulator of this kind is described, for example, in European Patent Application 866,221 A1. In common-rail injection systems a high-pressure pump, possibly with the assistance of a pre-supply pump, conveys the fuel to be injected from a tank into the central high-pressure fuel accumulator, which is known as the common rail. Fuel lines lead from the rail to the individual injectors associated with the cylinders of the internal combustion engine. The injectors are controlled individually by the engine electronic system as a function of the operating parameters of the internal combustion engine to inject fuel into the combustion chamber of the internal combustion engine.
The object of the present invention is to improve the quality and safety of the high-pressure connections in a high-pressure fuel accumulator of the type described in the preamble. In addition, the high-pressure fuel accumulator according to the present invention should have a simple design and should be inexpensive to manufacture.
This object is achieved with a high-pressure fuel accumulator for a common-rail fuel injection system of an internal combustion engine, having a tubular main body to which is welded at least one bushing for connecting a high-pressure line, by the fact that a collar is formed on the end of the bushing facing the main body.
The collar is used for introducing the welding current required for welding the bushing. In the case of conventional bushings without a collar, the welding electrode is applied to the end of the bushing facing away from the main body. In this case, welding splashes can enter the interior of the bushing and can damage a thread provided there. In addition, the geometry in the interior of the bushing may be deformed in an unwanted manner due to the temperatures that occur in welding. These disadvantages are avoided by providing the collar according to the present invention as a point of action for a welding electrode. Another advantage is that the collar forms a point of action for a force which presses the bushing against the main body during welding. Such a force can practically also be applied with the welding electrode.
A special embodiment of the present invention is characterized in that a bore leads from the interior of the tubular main body, opening into a receiving funnel which widens toward the outside and is used to receive one end of the high-pressure line which is pressed against the receiving funnel by an essentially hollow cylindrical press-screw so that it is tight under high pressure, and the seal is surrounded by an essentially hollow cylindrical insulation ring. An electric shunt is reliably prevented by the insulation ring when welding the bushing. In addition, the insulation ring prevents welding splashes from reaching the seal when welding the bushing.
Another special embodiment of the present invention is characterized in that the insulation ring is premounted in the bushing, and the inner lateral surface of the insulation ring is in contact with the outer lateral surface of a projection in which the receiving funnel is formed. This yields the result that the bushing is centered relative to the projection in assembly before welding.
Another special embodiment of the present invention is characterized in that the end of the high-pressure line is designed in a ball shape, and the inside diameter of the press-screw is larger than the outside diameter of the high-pressure line. This permits a clearance of the high-pressure line relative to the bushing. This yields the advantage that any installation tolerances in the engine compartment can be compensated.
Another special embodiment of the present invention is characterized in that the end face of the bushing which faces the tubular main body is tapered toward the inside. Due to this tapering, access to the connecting point between the bushing and the tubular main body is facilitated.
Additional advantages, features and details of the present invention are derived from the following description, in which two embodiments of the present invention are described in detail with reference to the drawing. The features mentioned in the claims and the description may be essential to the present invention either individually or in any combination.